Fix typo

README.md

@@ -110,7 +110,7 @@ Notes for DFM-17:
 
 * **DFM-17 radiosondes require a GPS lock (and clear visibility to the sky) to calibrate its internal oscillator.**
   This is necessary, because the internal oscillator is not particularly accurate.
-  DFM-17 transmissions, especially ARPS, may not decode correctly because of incorrect timing before
+  DFM-17 transmissions, especially APRS, may not decode correctly because of incorrect timing before
   the internal oscillator has been calibrated.
   * The RS41 radiosonde hardware uses an external oscillator, which is more stable, so RS41 does not
     suffer from the same issue.